Macro Engineering: PVdC blown-film die

Macro Engineering & Technology Inc., Canada has designed a seven-layer die, believed to be the first commercial-scale die for blowing film with PVdC. The die is made to produce film with nylon, EVA, LLDPE, LDPE, PVdC and a tie layer. The feedblock is designed to encapsulate the corrosive PVdC with EVA and special melt channels in the die that keep the EVA coating intact around the PVdC layer. Macro devised channels that change shape from teardrop to round, then square and back to a teardrop again. A new insulating air-gap device thermally isolates the 520 F nylon melt from the rest of the structure, which is at 370 F. The nylon joins the other layers just 0,5 in. before the die lip.

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